An energy unit refers to an engine system that produces energy for consumption. A combined cycle energy unit (CCEU) is an assembly of engines that work in tandem from the same source of energy (such as heat), converting it into mechanical energy, which in turn usually drives generators, such as electrical generators. The principle is that the exhaust of one engine (including heat) is used as the energy source for another, thus extracting more useful energy from the source, increasing the system's overall efficiency. Combining two or more thermodynamic cycles results in improved overall efficiency, reducing fuel costs. In stationary power plants, a widely used combination for a CCEU is a gas turbine burning natural gas or synthesis gas from coal, whose hot exhaust powers a steam power plant. This is called a combined cycle gas turbine (CCGT) plant, and such an arrangement is also used for marine propulsion. Other historically successful combined cycles have used hot cycles with mercury vapor turbines, magnetohydrodynamic generators or molten carbonate fuel cells, with steam plants for the second cycle.
In conventional CCGTs, there is a large amount of heat that leaves the system in the condenser or heat exchanger of system. The exhaust gases generated in a steam injected engine leave at a higher temperature and have a higher specific heat. Hence, in the absence of some form of heat recovery system, the overall efficiency of the engine decreases. Further gas turbine designs have included processes for recovering water from exhaust or flue gases and re-using the water in the gas turbine. The composition of modern gas turbine engines, however, cannot adequately withstand the introduction of corrosive substances and like materials. Therefore, gas turbine engine designs of this type have required a chemical water treatment apparatus to treat or distill the water before it is introduced back into the gas turbine engine, as taught by Inage (U.S. Pat. No. 7,594,387). The addition of a water treatment module, however, increases the complexity, maintenance and operating costs of the resulting gas turbine engine system.
Therefore, a need exists to overcome the problems with the prior art as discussed above, and particularly for more effective and efficient energy units.